Closure mechanism for chemical reaction kettle

ABSTRACT

An improved closure device for a laboratory scale chemical reactor which provides fast and efficient opening and closing of the reaction vessel as well as providing a simple and reliable system for relieving excessive pressure should it build up in the reaction vessel. The reactor is sealed by use of a substantially flat head that is seated against the rim of the reaction vessel by pressure which is generated by a variably adjustable closure means. Since the closure pressure can be adjusted to any value within the design limitations of the closure means, the closure means also operates as a pressure relief valve.

[0001] The present invention relates to reactors and methods for the synthesis of chemical compounds. Specifically, it relates to closure mechanisms for these reactors which permit the fast and efficient opening and closing of the reaction vessel. In addition, the present invention relates to a simple and reliable system for relieving excessive pressure should it build up in the reaction vessel.

BACKGROUND OF THE INVENTION

[0002] Reactors are used to synthesize various chemical products, such as polymers, from starting materials, commonly referred to as reactants. Industrial or full scale reactors subject these chemical reactants to certain, often unknown or unanticipated, chemical and physical conditions that are difficult if not impossible to imitate in small scale reactors used in laboratories. The synthesis chemist needs to know how a certain reaction might occur at the molecular level in an industrial sized reactor. Laboratory scale reactors perform this necessary service.

[0003] Certain laboratory scale equipment, such as reactor kettles, are universally used to create polymers. Traditionally, reactor kettles are spherically shaped and are made of glass. They have a plurality of openings or ports located on, when the reactor kettle is installed in its mounting bracket, its top side. These ports are used to hold in place tubes, usually sealed with stoppers, which are made out of either rubber or other substances that will not react with the material in the kettle. Chemical reactants may be delivered to the inside of the reactor kettle through feed tubes in the stoppers. Another port may house a thermometer or other sensing devices. Also, one of these ports will house the shaft of an agitator.

[0004] The problem with having to insert the agitator through the opening of the common reactor kettle port is that because of the narrow diameter of the port, only a very limited variety of agitator blade designs can be utilized. The most common agitator which can be used in reactor kettles consists of a blade which is loosely secured to the agitator by a pinion-type securing means. During insertion through the narrow diameter port, the blade must be aligned parallel to the agitator shaft. Then, once inside the reactor kettle, the operator must manipulate the agitator so that the blade rotates ninety degrees to the stirring shaft. This is a very labor intensive and time consuming operation and may require many attempts before the blade becomes oriented in the proper alignment to perform its intended function. These constraints limit the variety of blades which might otherwise be used to stir the reactants. As if the insertion process wasn't difficult enough, at the completion of the synthesis reaction, the agitator blade must then be oriented parallel to the agitator shaft so that the entire agitator can be removed from the reactor kettle for cleaning. The manipulation required to perform this process may be more time consuming, not to mention more frustrating for the operator, than the process of inserting the agitator blade into the reactor kettle in the first place.

[0005] Initial solutions to the problems presented by these substantially spherical, glass reactor kettles involved the design of a substantially cylindrical resin kettle having a large opening at the top, essentially of the same diameter as the internal reaction vessel. The reaction vessel is sealed by a cover or lid. These resin kettles may be jacketed, having one or more shells surrounding, but spaced apart from, the internal wall of the reaction vessel. The space between the shell and the vessel wall may be filled with circulating gas or liquid for cooling and/or heating purposes.

[0006] In certain industries, such as the food and pharmaceutical industries, cleanliness and the ability to continuously maintain the cleanliness of the resin kettle are critical. Even for many industrial applications, cleanliness is of the utmost importance where even the slightest amount of contamination may interfere with a reaction process. The inner surfaces of the reaction vessel are often coated with glass or other non-metallic, corrosion and/or temperature resistant material. Many of these materials, such as glass, tend to be relatively brittle and are prone to fracture upon impact or significant distortion.

[0007] The use of a reaction kettle with a lid as described above created other problems. In order to attach heads, covers, tops, fixtures, piping, etc. to these resin kettles, it is necessary to employ specialized joints which will substantially reduce the risk of harming these fragile coatings. These joints are designed to generally uniformly distribute stress, whether at ambient or elevated temperatures. The problems with simply adding joints to devices that perform chemical processes at elevated temperatures and under super-atmospheric pressure is that contaminants readily accumulate at such joints.

[0008] Traditional designs of such joints include two opposing, substantially parallel rigid surfaces having a gasket and/or other deformable material between them. In order to provide a sealed environment, a plurality of clamps or securing means are arranged around the perimeter of the lid to secure it to the reaction vessel. The structure which supports the securing means must be rigid enough to uniformly distribute a force, without distorting the joint surfaces, to effect the uniform compression of the gasket material in order to seal the two opposing surfaces. This force must be substantial enough to withstand the high internal pressures, and at elevated temperatures in some cases, that might be generated within the reaction vessel. Alternatively, the resin kettle may be used to conduct a reaction at ambient or even cryogenic temperatures and/or under sub-atmospheric.

[0009] The securing means of these resin kettles may be permanently, but movably, attached to either the lid or around the top rim of the vessel wall. Alternatively, they may be entirely separate and distinct from the joints formed between the abutting flanges. The time intensive task of removing or installing the lid or head is determined somewhat by the need to uniformly apply or relieve the pressure around the annular shaped abutting flanges. Traditional designs of securing means include exposed screw mechanisms, or over-riding cam mechanisms, all of which have multiple crevices, corners and pockets in which contaminants might build up. Contamination poses a significant problem which requires a great deal of time for cleaning.

[0010] Solutions to these problems are suggested in EP 0462383 B1 which discloses a chemical reactor vessel in which the securing means is not prone to contamination by the reactants in the vessel. A flange integral with the top rim of the reaction vessel is interposed between the securing means and the contents of the reactor so as to reduce the chances of contaminants accumulating at the securing means. However, while this disclosure might offer a seemingly more efficient system for maintaining the cleanliness of a laboratory resin kettle, it still utilizes one of the traditional systems for securing the lid to the reactor vessel, a screw mechanism. The opening and closing of the resin kettle described in this disclosure is still a very time consuming process.

[0011] Further, resin kettles using screw or cam type sealing mechanisms present an additional problem. Because the head or top portion of the resin kettle must be repositioned on the reactor vessel every time it is closed by the operator, it is difficult to insure that the head is positioned in the precise position for which it was designed in order to effect the best possible seal, even if the head is somehow hinged.

[0012] Another problem that must be addressed in the use of laboratory scale reactors is that of the need to relieve pressure if reaction conditions produce an excessive amount of pressure. Traditional means for relieving internal pressures comprise the use of one or more pressure relief valves, such as is shown in U.S. Pat. No. 4,682,622. Adding another device, such as a pressure relief valve located either on the reactor itself or to connecting pressure tubing connected to the resin kettle, adds to the complexity of the entire system. The pressure control valves are usually threaded into the wall of the reactor, or to a specially fitted plug. Due to different coefficients of expansion for the threaded portion of the pressure control valve and for the resin kettle or its threaded insert will contribute, over time, to the aggregation of contaminants. This, in turn, can cause the entire pressure control valve to become clogged be forcefully expelled from the reactor at an undetermined pressure. This uncertainty of reliable operation of the pressure control valve cannot insure the chemical integrity of the end product. Further, should the pressure relief valve become completely clogged by contaminants so as to render it useless for its intended function, it would probably fail to operate under super-atmospheric conditions, thereby increasing the risk of an explosive relief of pressure. What is needed therefore, is a closure and sealing mechanism for a laboratory scale chemical reactor that significantly improves productivity by enabling the rapid closure and opening of the reactor vessel, permits interchangeability between the reactor vessel and the head and eliminates the excessive building up of contaminants in the working parts and on the sealing interfaces of the reactor. In addition, what is needed is a simplified and more reliable pressure relief device. As shown below, the laboratory scale closure mechanism of the instant invention presents a novel solution to these problems.

STATEMENT OF THE INVENTION

[0013] In a first aspect, the chemical reactor closure mechanism of the present invention consists of a reaction vessel, having a rim at the top, a separable head, wherein the head is slideably connected to at least one vertically disposed guide shaft which permits the head to move only in a vertical direction; and, a closure means operatively connected to the head, wherein the closure means comprises

[0014] a drive cylinder,

[0015] a pressure source selected from either pneumatic or hydraulic systems, and

[0016] a pressure control means to regulate the amount of force exerted by the closure means to securely seal the head to the rim.

[0017] In a second aspect, the head functions as a pressure relief means.

[0018] In a third aspect, there is provided an improved method for sealing a laboratory scale chemical reactor, wherein the reactor comprises a reaction vessel having a rim at the top, a head having an inner surface positioned to face the interior of the reaction vessel, and a closure means, wherein a variable amount of force that is delivered by either a pneumatic or hydraulic pressure system is exerted on the head by the closure means. The force is infinitely adjustable within the pressure capabilities of the components of the closure means.

DETAILED DESCRIPTION OF THE DRAWINGS

[0019] In order to better show the present invention, the following drawings are provided. They are not intended to limit the scope of the invention to what is exemplified herein.

[0020]FIG. 1 is a semi-schematic, cross-sectional side elevational view of the laboratory scale reactor, showing the head in the closed position.

[0021]FIG. 2 is semi-schematic, cross-sectional side elevational view of the laboratory scale reactor, showing the head in the open position.

[0022]FIG. 3 is a semi-schematic, cross-sectional view of a portion of the laboratory scale reactor, showing a magnified image of the seal formed between the rim of the vessel and the head.

[0023]FIG. 4 is a semi-schematic, top elevational view of the laboratory scale reactor.

DETAILED DESCRIPTION OF THE INVENTION

[0024] The laboratory reactor 10 of the present invention consists of a reaction vessel 12, having an inner surface 14 and an outer surface 16. The circumferential rim 13 at the top of the reaction vessel 12 defines an opening through which reactants are added to and reaction products removed from the interior 22 of the reaction vessel 12. Positioned above and, during the processing of reactions, in contact with the rim 13 is the head 18. The head 18 is comprised of a substantially flat, rigid material capable of withstanding the compressive force necessary to seal the interior 22 of the reaction vessel 12 during chemical reactions without being deformed or fracturing. Suitable materials include cast steel, stainless steel, titanium and engineered polymeric resins, which may or may not be filled with glass or carbon particles.

[0025] The head 18 comprises two opposing surfaces, an interior head surface 20, which faces the interior 22 of the reaction vessel 12 and an exterior head surface 21. In order to provide an effective seal between the rim 13 and the interior head surface 20, it is necessary to add a deformable seal 23. The seal 23 may consist of any deformable material capable of effecting a tight seal, such as an O-ring. Preferred materials are elastomeric polymers. Further, in order to protect elastomeric polymers from chemical attack caused by contact with the reactants, an inert material, such as Pertetrafluoroethylene (PTFE), may be employed to coat the surface of the seal 23. The seal 23 sits in an annular channel 25 that is cut into or formed on the surface of rim 13 that faces the head 18. The annular channel 25 keeps seal 23 from moving and insures that when seal 23 begins to deform under the pressure exerted by the closing of the head 18 on the reaction vessel 12, the seal 23 maintains its position.

[0026] Chemical reactants 24, either in liquid, solid or gaseous form, may be added to the interior 22 of the reaction vessel 12 either all at once or sequentially, if required, as the reaction progresses. If the reactants are added prior to initiating the reaction, they may be placed into the interior of the vessel 22 while the head is removed. If, however, some of the reactants need to be added sequentially while the reaction is progressing, one or more feed tubes 38 may be positioned in the head 18. The feed tube 38 has an inlet 39 and an outlet 40, the outlet 40 projecting through the interior head surface 20 in order to deposit the sequentially fed reactants into the reactants 24 already present in the interior space 22 of the vessel 12. The feed tube 38 will be fitted with a means to seal off the feed tube when not in use so as to prevent releasing reactants or relieving pressure from the reaction vessel 12.

[0027] An agitator assembly 26 is used to provide mixing for the reactants 24. The portion of this assembly disposed in the interior 22 of the vessel 12 consists of an agitator output shaft 28 and an impeller 30. The output shaft 28 is sealably routed through a hole in the head 18 and is connected at its upper, or input end, to an agitator drive means 32. The agitator drive means may comprise any power source capable of providing rotational energy to the output shaft 28. However, an electric motor is considered most suitable. The agitator drive means 32 is supported above and in proximity to the exterior head surface 21 by an agitator mounting bracket 34.

[0028] Sensor 42 may be added to detect a variety of chemical and physical properties of the reactants 24 during the reaction process. Sensor 42 comprises a sensor shaft 44 which descends from the interior head surface 20 into the interior space 22 of the reaction vessel 12. At the end of the sensor shaft 44 which is located in the reaction vessel 12, is at least one detector 46. Of course, since it is desirable to monitor multiple characteristics of the reactants 24 during the reaction process, such as temperature, pH, various levels of certain ions, etc., a plurality of different detectors may be located at the end of the sensor shaft 44. The sensor shaft 44 is connected to a relay 50 which is removably secured to the head 18 by a sensor mounting bracket 48. Relay 50 compiles the raw data acquired from the plurality of detectors 46 and transmits it to a data processing and data storage device, such as a computer (not shown in the Drawings).

[0029] The vessel 12 is securely positioned by a reactor support bracket 51, which is, in turn, securely attached to a support base 52, generally referred to as the vessel assembly 53. This provides the reaction vessel 12 with the structural support needed during the processing of reactions or if detached from the rest of the components of the laboratory reactor 10. Support base 52 is releasably secured to conventional guide rails 69 and 69′ to insure accurate positioning of the support base 52 to head assembly 55. Head assembly 55 comprises the support structure for the head 18, and consists of substantially rigid material, such as steel or engineered resins. Optionally, a locking means, such as threaded or cam actuated devices may be employed to securely interlock head assembly 55 and vessel assembly 53. Since the guide rails 69 and 69′ insures the repeatability of the accurate alignment of the reaction vessel 12 and the head 18, multiple copies of the vessel assembly 53 can be produced for interchangeable use with a single head assembly 55. This vastly improves the speed of doing multiple reactions with the same head assembly 55.

[0030] In order to seal the laboratory reactor 10 during the reaction process, interior surface 20 of the head 18 is forcibly pressed against the top surface of rim 13 of the reaction vessel 12. At least one closure means 54 (two closure means are showed in FIG. 1 and FIG. 2, with the second one identified by the prime symbol) provides the pressure required to produce an effective seal. Closure means 54 comprises a drive cylinder 57 which is securely fastened to the base of the head assembly 55 by drive cylinder support shaft 59. Drive cylinder 57 is securely attached to head 18. The design exemplified by the Figures shows only one orientation of closure means 54. Another orientation, equally preferable, is for drive cylinder 57 to be securely attached to the base of head assembly 55 and for the drive cylinder support shaft 59 to be securely attached to the head 18. Securely attached to each end of drive cylinder 57 a pressure line or hose 56. The closure means shown in FIGS. 1 and 2 is intended to be exemplary. Any suitable hydraulic or pneumatic pressure cylinder design may be utilized. The underlying element is that the closure mechanism be attached to the head so as to separate it vertically from the reaction vessel, on the one hand, and be able to exert the pressure necessary to provide a seal between the head 18 and the top of the rim 13, on the other.

[0031] Hose 56 is shown in two segments, 56 a, which is connected to the lower end of the drive cylinder 57 and 56 b, which is connected to the top end of drive cylinder 57. Based on the exemplified design, in order to close the laboratory reactor 10, pressure is delivered from an external pressure source (not shown) and is routed via pressure line 68, through pressure control valve 60 and distributor 58, then through hose 56 b to drive cylinder 57 to exert a downward force on the head 18. The interface between the interior surface 20 of head 18 and the top of rim 13 thus forms a secure seal by compression of seal 23. When it is desired to open the laboratory reactor 10, pressure from the distributor 58 will be routed through hose 56 a, which then releases the pressure on the seal 23 and vertically raises the head 18. The use of pneumatic or hydraulic pressure systems provides that substantially an infinite number of pressure values may be selected by the closure means 54, limited only by the design limitations of the components of the laboratory scale reactor 10.

[0032] Closure means 54 provides the necessary energy to move the head 18 either up or down. In order to insure that the head 18 is placed precisely at the same location on the rim 13, guide shafts 63 and 65 are used. These guide shafts 63 and 65 are securely attached to the base of the head assembly 53. Each are slideably engaged with the head 18 to permit only the vertical movement of the head 18.

[0033] By having the capability to adjust the amount of pressure which holds the head and reaction vessel together, the closure means 54 is able to perform the function of a pressure relief valve. The reactor operator may adjust the pressure exerted by the closure means 54 to a predetermined constant amount, sufficient to hold the head 18 in its closed position on the rim 13 of the reaction vessel 12. Any pressure that might build up in the reaction vessel 12 that generates a force higher than the force which securely engages the head 18 to the reaction vessel 12 during processing will cause the seal to rupture, thereby relieving the buildup of pressure in the reactor. This is desirable to having excessive pressure build up in the reaction vessel 12 and risking the possibility of an explosion.

[0034] Having disclosed the advantages of the improved laboratory chemical reactor closure mechanism, the following now sets forth the boundaries of the claimed subject matter. 

We claim: 1) A closure device for a laboratory chemical reactor comprising: a reaction vessel, wherein the reaction vessel has a rim at the top; a head, wherein the head is slideably connected to at least one vertically disposed guide shaft, wherein the at least one guide shaft permits vertical travel of the head; and closure means operatively connected to the head, wherein the closure means comprises: a drive cylinder, a pressure source selected from the group consisting of hydraulic and pneumatic pressure systems; and pressure control means to regulate the amount of force exerted by the closure means to sealably engage the head and the rim of the reaction vessel. 2) The closure device of claim 1 wherein the rim comprises an annular channel. 3) The closure device of claim 1 wherein the closure means further comprises a pressure relief means. 4) The closure device of claim 1 wherein the closure means urges the head to travel vertically up or down along the at least one guide shaft. 5) A method for sealing a laboratory scale reactor, wherein the reactor comprises a reaction vessel, said reaction vessel having a rim at the top, a head, said head having an interior surface and an exterior surface, and a closure means which comprises a drive cylinder and a pressure source selected from the group consisting of hydraulic and pneumatic pressure systems; the improvement comprising: urging the head to sealably engage the rim of the reaction vessel under pressure provided from the pressure source to the closure means; and applying pressure from the drive cylinder to generate sufficient force to effect a seal between the rim of the reaction vessel and the interior surface of the head. 6) The method of claim 5 wherein the force is infinitely adjustable. 7) The method of claim 5 wherein the pressure is adjustable to apply the amount of force necessary to enable the closure means to function as a pressure relief means. 